Fire resistant hydraulic fluid



FIRE RESISTANT HYDRAULIC FLUID Raymond B. Tierney, Beacon, Richard K. Meyers, Wappingers Falls, and Robert H. Krug, Cornwall, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed July 12, 1956, Ser. No. 597,352

9 Claims. (Cl. 252-78) This invention relates to a fire resistant hydraulic fluid. More particularly, it concerns a water-in-oil emulsion having a specific composition rendering it excellent for use in the process of transmitting power without danger of fire.

In recent years the increased emphasis on industrial safety programs has resulted in a growing awareness on the part or industry that large volumes of mineral hydraulic oils in exposed areas constitute a dangerous safety hazard with respect to fires and explosions. A number of different solutions to the problem have been considered. These consisted of the use of various types of compositions which were intended to duplicate the performance of a mineral oil hydraulic fluid without the accompanying fire hazard. As will be pointed out hereafter, none of these compositions were satisfactory in meeting modern requirements. This invention, however, consists of an improved hydraulic fluid which duplicates mineral oil performance in the process of transmitting power without fire hazard and is. not subject to the objections raised against prior art products.

The improved fire resistant hydraulic fluid of this invention is a water-in-oil emulsion comprising from 60 to 40 volume percent of water in the internal phase and from 40 to 60 percent of an oleaginous blend containing a major portion of mineral oil having an upper viscosity limit of 300 SUS at 100 F. in the external phase, at least 4.0 and up to about 12.0 volume percent of an emulsifying agent selected from the group consisting of fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides, alone, in mixtures and in combination with no more than 20 percent, based on the emulsifying agent, of uolyoxyalkylene derivatives of fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides, said fatty acids having from 6 to 30, preferably from 12 to 24, carbon atoms, and a volatile corrosion inhibitor in an amount sufiicient to inhibit corrosion by the emulsion while in the vapor and liquid phases. Preferably, in order to meet the performance standards of inhibited mineral oil hydraulic fluids, the emulsion contains a minor amount of an antiwear agent and a minor amount of an antioxidant for the oil phase of the emulsion. In addition, an antifoam agent and a pour point depressant have also been found to be extremely useful.

As previously stated, prior to the present invention, various types of compositions were tried which were found to have serious drawbacks. The compositions included: 1) mineral oil plus snuflFers, (2) all synthetic fluids, (3) water-glycol base fluids, (4) oil-in-water emulsions.

Mineral oil plus snuffers were considered unsatisfactory when it was found that the smiling agents, hexachlorobutadiene and tetrachloroethane, for example, even when present in lar e quantities up to 50 percent had only a very slight effect on the flammability of the mineral oil and at such concentrations rendered the compositions highly toxic.

2,965,574 Patented Dec. 20, 1960 The all synthetic fluid tried also was unsatisfactory when it was found that certain components exhibited excessive toxicity. Other known less toxic all synthetic fluids are expensive and deleteriously affect seal materials.

Water-glycol base hydraulic fluids were found to be less objectionable in use than the preceding type fluids, however, none of the water-glycol base fluids tested came close in performance to a mineral oil hydraulic fluid. This type of fluid is also quite expensive in comparison to a mineral oil hydraulic fluid.

The fourth type of hydraulic fluid considered, namely, oil-in-water emulsions containing from 3 to 50 volume percent mineral oil, was entirely unsatisfactory in the pump type screening test because it failed to lubricate satisfactorily and consequently further consideration was not given to its use.

The high amount of water in the emulsion of .the present invention is of the essence in order to guarantee a fire resistant fluid. The standard was set as a result of testing emulsions containing various amounts of water in the Spray Ignition Test defined by the military specification designated MIL-F-7100. This test consists of forcing the test fluid through a small orifice under 1000 pounds pressure. The resulting spray is directed through the heart or hottest part of an oxy-acetylene torch. The torch is moved from 4 to 18 inches from the orifice. Between these distances there should be no evidence of flame propagation either downstream or upstream from the torch. Localized burning in the near vicinity of the torch is acceptable, however, providing no flame propagation occurs. The results of this test on emulsions having the same oil blend comprising 88.7 (vol.) percent of a paraflin base oil having a viscosity of SUS at R, an emulsifier consisting of 5 (vol.) percent of sorbitan monooleate and 1 (vol.) percent of a polyoxyethylene derivative of sorbitan monolaurate, 5 (vol.) percent of tricresylphosphate, 0.3 (vol.) percent of a 50 percent concentrate of 2-hydroxypropylaminen trite. 0.3 (wt) percent of 4-methvl-2.6-di-tertiary butylphenol, and p.p.m. of dimethyl silicone in a 10 percent kerosine solution emulsified with various amounts of deionized water are set forth in the following table.

The results as indicated in Table I definitely. show that at least 40 percent water is necessary to produce a satisfactory fire resistant fluid with this oil blend. The upper limit of water (60%) present in the emulsion represents a safety limit to prevent a reversal of the emulsion and an accompanying drastic loss of viscosity. Within this relatively small given range (40-60%), different concentrations of water will not greatly effect the excellent properties of the emulsion. An increase in the water content, however, will cause an increase in viscosity until the point of emulsion reversal occurs, which is beyond the upper limit of water content of the invention.

Any type of mineral oil or mixture thereof is useful in accordance with this invention as long as the viscosity of the oil does not exceed 300 SUS at 100 F. The pre- .fcrred type of mineral oil is one having a viscosity of from 50 to 100 SUS at 100 F., a flash point ranging from 300 to 375 F., and a pour point of not more than +20 F. Since at least 40 volume percent of water is required to render the emulsion fire resistant, the oil component,

of necessity, must meet a low viscosity requirement, so that when mixed with water the resulting fluid is not excessively viscous thus preventing its usefulness as a hydraulic fluid.

The preparation of a water-in-oil emulsion with the and 'no heat was necessary. Heating was, however, em- 20 ployed when necessary. While the 'oil and emulsifier were being agitated, 50 volume percent of deionized water was added in a small but steady stream. Agitation was polyoxypropylene, and polyoxybutylene derivatives of the fatty acid partial esters of hexitans and hexides. Some examples of the fatty acids useful when chemically combined to form partial esters in accordance with the present 'nvention are caproic, sorbic, pelargonic, capric, lauric, myristic, palmitic, margaric, stearic, oleic, linoleic, linolemc, arachidic, behenic, cerotic, and melissie. The preferred emulsifying agent is the combination of sorbitan monooleate and a polyoxy ethylene derivative of sorbitan monolaurate.

Mixtures of the same fatty acid partial esters of a hexitan and a hexide are commonly referred to merely as hexitan monoesters and are included within the scope of the invention. These mixtures, in many instances, have superior emulsifying properties and are less expensive than the pure compounds.

When a combination of fatty acid ester and polyoxyalkylene derivatives thereof is used as an emulsifying agent, it is imperative that no more than percent of t e polyoxyalkylene derivative be present in the combina tion. This limitation results in a balanced hydrophilic lipophilic emulsifi-r which lends excellent stability to the emulsion. This is demonstrated in the following table.

Emulsifying Agents (1) Sorbitan monooleate polyoxyethylene derivative of sorbitan monolaurate (2) Sorbitan monooleate olyoxyethvlene derivative of sorhitan rnonolaurate (3) Sorbitan monooleate polvoxycthylene de ivative of sorbitan monolauratenu;

(4) Sorbitan monooleate polyoxyethylene derivative of sorbitan monolaurate (5) Sorbitan monooleate (6) Sorbitan monooleate Table II Separating Vol. percent Vol. percent Time and Degree of Emulslfler of Emulsifier component based on oil Room Temp. 150 F.

a s 1 h 12 h 3o eparationin ass I: an ours. 6 After2 weeks no sepa- After 2 weeks very ration. slight oil separation, 90 no water separation. 10 10 After 3 months trace After 3 weeks 10% oil of oil, slight trace of separation, no water 90 water. separation. 10 5 After 4 months trace After 5 weeks 10% 011 of oil, silght trace of separation, no water water. 1 separation. 100 5 After '4 months After 5 weeks '40%-o11 oil separated, no separation, no water Water separation. se aration. 100 10 After '4 months 10% After 5 weeks 40% 011 oil separated, 'no separation, no Water water separated. separation.

continued for five minutes after the water addition was complete. The emulsion was then allowed to stand overnight. If separation occurred during this period, the mixture was discarded. If little or no separation occurred, the emulsion was subjected to storage testing which was carried out at room temperature and in a 150 F. heated oven. Periodic inspection of the emulsions were made during which the amount of separated oil and water was noted. Those emulsifiers which caused the emulsion to shovdv little separation after three weeks were considered goo v The emulsifying agents which were found to be suitable in accordance with this invention included a fatty acid partial ester of a six carbon 'polyhydric alcohol monoor di-anhydride which is essentially lipophilic either alone, in mixtures with the same type of compound or in combination with a polyoxyalkylene derivative of a fatty acid partial ester of a six carbon polyhydric alcohol monoor dianhydride which is essentially hydrophilic. The fatty acid portion of the ester having from 6 to 30 carbon atoms and the alkylene group of the polyoxyalkylene derivative having from 1 to 4 c r on atoms. Examples of lipophile emulsifying agents include the partial esters of sorbitan. sorbide. mannitan, mannide, dulcitan, and dulcide; These compounds. per se, and the method of producin them are set forth in US. Patents 2 322.820 and'2.322.82l. Examples of the hydrophile emulsifying agents include the polyoxymethylenc, polyoxyethylene,

It is seen from the foregoing Table II that the emulsifying agent in'No. 1 having well over 20 percent of a polyoxyalkylene derivative present in the combination produced no appreciable emulsion stability, whereas those having less than 20 percent and particularly those having about '10 percent were excellent stability producers. Emulsifying agents Nos. 5 and 6 wherein no polyoxyethylene derivatives were combined lent good stability to the emulsion although they were somewhat 'less effective than the preferred emulsifier combination.

It is pointed out that while the emulsion used herein to demonstrate the superior water in-oilemuls ion properties were made with deionized water, ordinary tap water may also be used so long as it does not contain a high percentage of metal carbonates, such as calcium carbonate or bicarbonate. Tap water emulsions with low earbonate content showed slightly less emulsion stability on storage, 'however, they were none-the-less adjudged to be satisfactor for use in hydraulic systems.

Owing to the large amount of water present in the emulsion. it was found absolutely necessary to incorporatea voa ile rust inhibitor to prevent the rusting of the metal p rts of t e hydraulic system with which the fluid, in both liquid and vapor phases, .came in contact. Without such an inhibitor the system would soon become choked with rust necessitating renewal of parts and c ang nq of the fluid. The class of a'nirust agents which is useful is the amine nitrates andam-ine carboxylates.

These compounds are excellent two-phase rust inhibitors and are useful in amounts of from 0.05 to 1.0 (vol.) percent based on the oil phase of the emulsion. Examples of such compounds include Z-hydroxypropylamine nitrite, isopropylamine nitrate, cyclohexylamine nitrite, diisobutylamine nitrite, triethylamine nitrite, amylamine benzoate, diisopropylamine benzoate, monoethanolamine benzoate, isoamylamine salicylate, and diisopropylamine butylphosphonate. The preferred rust inhibitor which is used in accordance with this invention is Z-hydroxypropylamine nitrite due to availability and cost. This compound has given excellent rust protection to metal parts of the hydraulic test systems in both the liquid and vapor phase despite tthe large amount of water present.

In order to obtain a fire resistant fluid which is comparable to inhibited mineral oils with respect to wear properties, it is necessary to incorporate a compatible antiwear agent in the emulsion. Hydrocarbon phosphate esters have been found to be the most satisfactory antiwear agents. These compounds, for example, diand triphenyl phosphates, tricresylphosphate, tributyl phosphate, triethyl phosphate, trioctyl phosphate, and a mixture of monoand dialkyl phosphoric acid esters wherein the alkyl group is a straight chain containing from 8 to 16 carbon atoms, are incorporated in amounts up to 10 volume percent based on the mineral oil. The preferred antiwear agent on the basis of availability is tricresylphosphate in an amount ranging from 0.5 to 10 percent by volume based on the oil blend. It is preferably present in the emulsion in the amount of about 5 (vol.) percent based on the oil. The low concentration of the tricresylphosphate eliminates any question of toxicity and adds many hours of Wear to the moving parts which contact the fluid.

An antioxidant is also an extremely useful additive in the emulsion to prevent breakdown of the oil phase after continued use. Oxidation of the oil causes it to become excessively acidic and thus harmfully corrosive. This acidic oil will also seriously effect the stability of the emulsion. The antioxidants which have been found to be particularly useful in accordance with this invention are the so-called partially or totally hindered phenols. Such compounds are characterized by the presence of particular organic groups in a certain position on the phenolic portion of the molecule which serve to inhibit a reaction or cause steric hindrance. Compounds which meet the foregoing characterization are represented by the following structural formula:

wherein R, R, R", and R' represent hydrogen, alkyl and aralkyl, and wherein at least one of the groups in the ortho position relative to the oxy group contains at least three carbon atoms. The total number of substituent carbon atoms should be sufiicient to prevent solubility of the compounds in Water. Examples of these compounds include: 4-methyl-2,6-di-t-butylphenol; Z-t-butyl- 4,6dimethylphenol; 2,4,6-t-tributylprenol; 2,6-di-t-amyl- 4 t butylphenol; 2,4 dimethyl 6 propylphenol; t-butyl ether of o-sec-butyl-p-cresol; t-butyl ether of o-sec-butyl-p-ethylphenol; t-amyl ether of o-sec-butyl-pisobutylphenol; mixtures of oand p-polyalkylbenzylphenol.

Other compounds which are classified as hindered phenols and which are useful with the present invention are the alkylene bis alkyl phenols having the following structural formula:

B5 II wherein R is a hydrogen, alkyl or aralkyl radical, R is a hydrogen or alkyl radical, and R R and R are hydrogen, hydroxy, amino, halogen, alkyl, aryl, or aralkyl radicals. Examples of such compounds are: 1,1-bis (2-hydroxy-3-t-butyl-5-methylphenyl)ethane; 2,2-bis (2- hydroxy-3-t-butyl-5-methylphenyl)n-propane; 1,1-bis (2- hydroxy-3,S-di-t-butylphenyl)n-butane; 2,2-bis (2-hydroxy-3-t-butyl-5-methylphenyl) -2-tri-fiuorethane; 1,1-bis- (2-hydroxy-3,5-di-t-butylphenyl)methane.

These antioxidant additives are incorporated in the oil component or blend of the emulsion in amounts up to 1 percent by Weight and preferably in an amount of about 0.3 (wt) percent. The preferred additive is 4- methyl-2,G-di-t-butylphenol on the basis of availability and cost. The preferred compound is sometimes referred to as di-t-butyl-p-cresol.

Initial water-in-oil emulsions tested were found to give somewhat more foam on agitation than was believed desirable. Thus an antifoam additive, preferably a 10 percent solution of dimethyl silicone in kerosine, was added in the amount of 150 p.p.m. to the oil phase of the emulsion with excellent results. No further trouble with foaming was encountered.

In evaluating the emulsion of the present invention a test generally referred to as the Vickers Pump Test is employed. The apparatus used in this test is a hydraulic system which functions as follows: Oil is drawn from a closed sump through a Cuno Type EG Auto-Kleen filter to the intake side of a Vickers V-104A vane-type pump. The pump is driven by, and directly coupled to, a five horsepower, 1740 r.p.m. electric motor. The oil is discharged from the pump through a Vickers Model CT-06-B10 pressure regulating valve. From there it passes through a calibrated venturi (used to measure flowrate) and back to the sump. Cooling of the oil is accomplished by passing cold water through aluminum coils immersed in the sump. No external heat is required, the temperature being raised by the frictional heat resulting from the pumps work on the oil. The sump is air-vented through a calcium chloride dryer. The Vickers V-104A vane-type pump comprises a cylindrical enclosure which houses a so-called pump cartridge. The pump cartridge assembly consists of front and rear circular plates having center shaft supporting circular openings and fluid inlets disposed therein. These shaft support openings are provided with bronze bushings. A rotor is supported for rotation between the front and rear plates by the insertion of its shafts or axes within the front and rear bushings. A plurality of removable vanes are inserted into slots in the periphery of the rotor. A ring or stator member encircles the rotor and encloses it within the two plate members. The inner surface of the ring is cam shaped to enable a rotary pumping action by the vaned rotor against the cam surface.

The Vickers Pump Test procedure in the present case consisted of charging the system with three gallons of the test fluid and running at temperatures ranging from to F. at 1000 p.s.i. pump discharge pressure. Wear data were made by weighing all the components of the pump cartridge individually, except for the vanes which were grouped. At the conclusion of the test run and upon disassembly for weighing, visual examination of the system was made for signs of deposit,

varnish, corrosion, etc.

7 'I'he'following table shows the results of the cartridge weight loss in the Vickers Pump Test on an inhibited emulsion consisting of 50 percent deionized water and 50 percent of an oil blend consisting of 88.7 (vol.)

atoms, and a volatile corrosion inhibitor inan amount sufficient to inhibit corrosion in both the liquid and vapor phases.

percent of a paraflin base oilhaving an SUS viscosity '5 2. The fire resistant water-in-oil emulsionof claim"1 of 70 to 75 at 100 F., a pour of +20 F. and a V.I. wherein'the lipophilic emulsifying agent is selected from of 75; .0 (vol.) percent of sorbitan monooleate; 1.0 the group consisting of fatty acid partial esters of sorbitan (vol.) percent of a polyoxyethylene derivative of sorbitan and sorbide, and mixtures thereof, in combination with monolaurate; 5.0 (vol.) percent of tricresylphosphate; from about 10 percent to 20 percent of polyoxyethylene 0.3 (vol.) percent of a 50 percent concentrate of 2- l0 derivatives of fatty acid partial esters of sorbitan and hydroxypropylaminenitrite; 0.3 (wt.) percent of 4- sorbide, said fatty acids having rom 12 to 24 carbon methyl-2,6-di-t-butylphenol; and 150 ppm. of a dimethyl atoms, and said volatile corrosion inhibitor is selected silicone polymer-in a 10 percent kerosene solution. from the group consisting of amine nitr tes and amine The results of this test on an inhibited mineral oil carboxylates in an amount-ranging from0.05 to 1.0 volare shown for comparison. The mineral oil used Was 15 ume percent. a paratfin base oil having an SUS viscosity of 150 at 3. A fire resistant water-in-oil emulsion of claim 2 100 F., a pour of -10 F. and a V.I. of 97. This which a so contains a wear inhibiting hydrocarbon phosoil was inhibited with approximately 0.3 (wt) percent phate ester in an amount ranging from 0.5 to 10 volof the antiox dant 4-methyl-2,6-di-t-butylphenol, apume percent based on said blend, and an oxidation inproximately 0.033 (wt.) percent of an anti-rust 50-50 hibiting hindered phenol in an amount ranging up to mineral oil concentrate comprising a mixture of mono- 1.0 weight percent ba ed on said blend. and dilauryl phosphoric acid esters, and about 0.001 4. A fire resistant water-in-oil emulsion suitable for percent of an antifoam 10 percent kerosene concentrate use as a hydraulic fluid consisting essentiallyof about of a dimethyl silicone polymer. 50 volume percent of water and about .50 volume per- Table III Running Front and Cam Test Fluid Time (hrs) Rear Bush- Rotor Ring Vanes Total ings,Total Inhibited Mineral oil:

Rum 500 0.091 0.018 0.034 0.448 0. 591 703 0.428 +0.337 9.998 0.137 10.220 s00 0.117 +0.023 0.114 0.017 0.225 -Run2 1.000 0.137 0.000 0.125 0.018 0.286 1,770 0.222 0.007 11.826 0.328 12. 009 Inhibited Emulsion =1, 500 0.463 0.001 0.289 0.076 0.820

1 Cartridge disassembled, weighed and reassembled. 1 Hours to failure. Cartridge re laced.

The above table demonstrates that the emulsion of the present invention compares very favorably in cartridge wear to the inhibited mineral oil. On disassembling, the overall condition of the pump system was seen to be excellent. There was no trace of rust below or above the fluid level and no sludge or deposit formation anywhere attesting to the effectiveness of the additives incoporated in the emulsion.

Further evidence that the emulsion of this invention is very satisfactory as a hydraulic fluid lies in the fact that it has been tested in the field by use in a production model welder continuously for over eight months with satisfactory performance without accompanying fire hazard.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made Without departing from the spirit and scope thereof and,

therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A fire resistant water-in-oil emulsion suitable for use as a hydraulic fluid consisting essentially of from 60 to volume percent of water and from 40 to 60 volume percent of an oleaginous blend containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F., from 4 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of fatty acid partial esters of six carbon polyhydric alcohol monoand d anhydrides, and mixtures thereof, in combination with from about 10 percent to 20 percent, based on said lipophiic emulsifying agent, of polyoxyalkylene derivatives of fatty acid partial esters of six carbon polyhydric alcohol monoand dianhydrides, said fatty acids having from 6 to 30 carbon atoms, and the alkylene portion of said cent of an oeaginous blend containing a major portion. of mineral oil having a viscosity in the range from about 70 to about 150 SUS at F., from 4 to 12 volumepercent of an emulsifying agent consisting essentially of an oleic acid monoester of sorbitan in combination with about 10.0 volume percent based on the emulsifying agent of a polyoxyethylene derivative of a lanric acid monoester of sorbitan, about 0.15 volume percent of a hydroxypropylamine nitrite, about 5.0 volume percent of tricresyl phosphate, about 0.3 weight percent of 4- methyl-2,6-di-t-butylphenol, and from 100 to 200 ppm. of a 10 percent kerosine solution of dimethylsilicone polymer.

5. A fire res stant water-in-oil emulsion suitable for use as a hydraulic fluid consisting essentially of from 60 to 40 volume percent of water and from 40 to 60 volume percent of an oleaginous b end containing a major portion of a mineral oil having a viscosity in the range from 50 to 300 SUS at 100 F., and from 4 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of fatty acid partial esters of 6-carbon polyhydric alcohol monoand dianhydrides. and mixtures thereof, in combination with from about 10 percent to 20 percent based on said lipophilic emu sifying agent, of polvoxyalkylene derivatives of fatty acid partial esters of 6-carbon polyhydric alcohol monoand dianhydrides, said fatty acids having from 6 to 30 carbon atoms, and the alkylene portion of said polyoxalkylene derivatives having from 1 to 4 carbon atoms.

6. The process which comprises transmitting power in a hydraulic system by means of awater-in-oil emulsion comprising from 60 to 40 volume percent of water and from 40 to 60 voume percent of an olea inous blend containing a major portion of a mineral o'ilhavingan 9 upper viscosity limit of 300 SUS at 100 F., from 4 to 12 volume percent of a lipophilic emulsifying agent selected from the group consisting of fatty acid partial esters of six carbon polyhydric alcohol mono,- and dianhydrides, alone, in mixtures and in combination with no more than 20 percent, based on said lipophilic emulsifying agent, of polyoxalkylene derivatives of fatty acid partial esters of six carbon polyhydric alcohol monoand diananhydrides, said fatty acids having from 6 to 30 carbon atoms, and the alkylene portion of said polyoxyalkylene derivative having from 1 to 4 carbon atoms, and a volatile corrosion inhibitor in an amount sufiicient to inhibit corrosion in both the liquid and vapor phases.

7. The process of claim 6 wherein the lipophilic emulsifying agent is selected from the group consisting of fatty acid partial esters of sorbitan and sorbide, alone, in mixtures and in combination with no more than 20 percent of polyoxyethylene derivatives of fatty acid partial esters of sorbitan and sorbide, said fatty acids having from 12 to 24 carbon atoms, and said volatile corrosion inhibitor is selected from the group consisting of amine nitrates and amine carboxylates in an amount ranging from 0.05 to 1.0 volume percent.

8. The process of claim 7 wherein said oleaginous blend contains a wear inhibiting hydrocarbon phosphate ester in an amount ranging from 1 to 10 volume percent based on said blend, and an oxidation inhibiting hindered phenol in an amount ranging from 0.001 to 1.0 volume percent based on said blend.

9. The process which comprises transmitting power in a hydraulic system by means of a water-in-oil emulsion comprising about 50 volume percent of water and about volume percent of an oleaginous blend containing a major portion of mineral oil having an upper viscosity limit of 150 SUS at F., from 4 to 12 volume percent of an emulsifying agent consisting essentially of an oleic acid monoester of sorbitan in combination with about 10.0 volume percent based on the emulsifying agent of a polyoxyethylene derivative of a lauric acid monoester of sorbitan, about 0.15 volume percent of a hydroxypropylamine nitrite, about 5.0 volume percent of tricresyl phosphate, about 0.3 weight percent of 4-mcthyl-2,6-di-t-butylphenol, and from 100 to 200 p.p.m. of a 10 percent kerosine solution of dimethylsilicone polymer.

References Cited in the file of this patent UNITED STATES PATENTS 2,023,367 Krekeler Dec. 3, 1935 2,558,030 Zisman June 26, 1951 2,559,583 Barker July 10, 1951 2,583,588 Mosteller Jan. 29, 1952 2,661,334 Lummus Dec. 1, 1953 2,689,219 Menaul Sept. 14, 1954 2,710,842 Heisig et al. June 14, 1955 2,744,870 Stillebroer et al May 8, 1956 FOREIGN PATENTS 617,404 Great Britain Feb. 4, 1949 496,875 Canada Oct. 13, 1953 OTHER REFERENCES Atlas Surface Active Agents by Atlas Powder Co. (1948), pp. 3839.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO, 2365, 574 December .20 1960 Raymond B o Tierney et .2110

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 75,, for finittrretes" read nitrites column 5 line 5, for nitrate read nitrite Signed and sealed this B lstdayiof July 1962a (SEAL) Attest:

ERNEST w. SWIDER v AVID L- LADD Attesfing Officer 7 Y Commissioner Of Patents 

1. A FIRE RESISTANT WATER-IN-OIL EMULSION SUITABLE FOR USE AS A HYDRAULIC FLUID CONSISTING ESSENTIALLY OF FROM 60 TO 40 VOLUME PERCENT OF WATER AND FROM 40 TO 60 VOLUME PERCENT OF AN OLEAGINOUS BLEND CONTAINING A MAJOR PORTION OF A MINERAL OIL HAVING VISCOSITY IN THE RANGE FROM 20 TO 300 SUS AT 100*F., FROM 4 TO 12 VOLUME PERCENT OF A LIPOPHILIC EMULSIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF FATTY ACID PARTIAL ESTERS OF SIX CARBON POLYHYDRIC ALCOHOL MONO- AND DIANHYDRIDES, AND MIXTURES THEREOF, IN COMBINATION WITH FROM ABOUT 10 PERCENT TO 20 PERCENT, BASED ON SAID LIPOPHILIC EMULSIFYING AGENT, OF POLYOXYALKYLENE DERIVATIVES OF FATTY ACID PARTIAL ESTERS OF SIX CARBON POLYHYDRIC ALCOHOL MONO- AND DIANHYDRIDES, SAID FATTY ACIDS HAVING FROM 6 TO 30 CARBON ATOMS, AND THE ALKYLENE PORTION OF SAID POLYOXYALKYLENE DERIVATIVE HAVING FROM 1 TO 4 CARBON ATOMS, AND A VOLATILE CORROSION INHIBITOR IN AN AMOUNT SUFFICIENT TO INHIBIT CORROSION IN BOTH THE LIQUID AND VAPOR PHASES. 